Drug delivery device

ABSTRACT

There is provided drug delivery devices comprising a drug container assembly with a needle and automatic needle insertion and drug delivery mechanisms. Aspects of the devices described include a noise-generation mechanism to indicate the completion of drug delivery, a mechanism for triggering drug delivery following needle insertion, front-end activation of the device and a safety mechanism for covering the needle after use and methods of assembly of the devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/908,439, filed Jan. 28, 2016, titled DRUG DELIVERY DEVICE, which is aU.S. National Stage Application under 35 U.S.C. § 371 of InternationalApplication No. PCT/GB2014/052282, filed Jul. 25, 2014, titled DRUGDELIVERY DEVICE, which claims priority to United Kingdom PatentApplication No. GB 1313782.3, filed Aug. 1, 2013. U.S. patentapplication Ser. No. 14/908,439 and International Application No.PCT/GB2014/052282 are each incorporated by reference herein in theirentirety.

FIELD OF THE INVENTION

The present invention relates to devices for administering drugs topatients, and in particular to autoinjectors.

BACKGROUND TO THE INVENTION

An autoinjector is a drug delivery device that contains a medical,therapeutic, diagnostic, pharmaceutical or cosmetic compound (drug)before it is administered, and which is used to administer the compoundthrough the skin of the patient via a hollow needle. Autoinjectors maybe used by the patient themselves or by a different user, and may beused to administer drugs to animals.

Autoinjectors are typically used because they reduce the amount oftraining and effort needed by a user compared with that needed for asyringe, by automating either or both processes of inserting the needleinto the patient and expelling the drug through the needle. They canalso reduce the fear of injection by hiding the needle from the patientand protect the patient from needle stick injuries.

Autoinjectors typically include a housing containing a drug and aplunger that is driven by an automatic mechanism to move the plungerwithin the housing to eject the drug. The automatic mechanism may alsomove the needle relative to the housing to insert the needle into asubject. Motive power for the mechanisms may come from one or moresprings or other power sources such as compressed gas.

Autoinjectors are used to deliver so-called crisis drugs such asepinephrine, where a patient may need to self-inject the drug whileunder the severe stress of anaphylactic shock. They are also used todeliver drugs for long-term conditions such as rheumatoid arthritis,where the patient may have limited dexterity.

In both cases it is beneficial for the autoinjector to have a simple andeasy user interface in order to maximise the likelihood that the patientis able to operate the autoinjector correctly and receive the drug. Itwould also be desirable to provide an audible indication to the patientthat drug delivery has been successfully completed.

It is also desirable for the autoinjector to be small, reliable androbust, simple to manufacture, secure during transport and beforeintended use, and suitable for drugs having high viscosity.

SUMMARY OF THE INVENTION

The invention is defined in the appended independent claims, to whichreference should be made. Advantageous features are set out in thedependent claims.

In a first aspect, there is provided a drug delivery device comprising:

a drug container containing a drug;

a plunger within the drug container, movement of the plunger within thedrug container being operative to deliver the drug from the drugcontainer; and

a drive mechanism, the drive mechanism comprising: a stored energysource, the stored energy source configured to release energy byexpanding from a compressed state, a first drive element coupled to thestored energy source, and a second drive element coupled to the firstdrive element and positioned between the first drive element and theplunger, wherein in a first position of the drive mechanism the firstdrive element is constrained from moving in an axial direction relativeto the second drive element but in a second position of the drivemechanism the first drive element is free to move in the axial directionrelative to the second drive element such that a first surface of thefirst drive element is driven against a first surface of the seconddrive element by the stored energy source to produce an audible signalindicative of the completion of drug delivery from the drug container.

Previous mechanisms used to provide an audible indication of completionof drug delivery in drug delivery devices have suffered from the problemthat the audible indication has not been loud enough. They havetypically relied on a portion of the drive element used to drive thedrug out of the device striking a stationary part of the device housingas it moves past that stationary part. The solution of the presentinvention is to use a stored energy source to drive two parts of amulti-part drive mechanism against each other when the drive mechanismreaches a predetermined position within the device. This allows a muchgreater noise to be generated as the parts can be made rigid and may bedriven against each other at high speed.

Advantageously the expansion of the stored energy source moves the drivemechanism from the first position to the second position.

In order to constrain the first drive element from moving in the axialdirection relative to the second drive element in the first position, afurther component within the drive mechanism, which interacts with anexternal component of the device, may be used. Alternatively, anexternal component of the housing through which the drive mechanismmoves may be used to interact with the first or second drive element toconstrain relative axial movement between the first and second driveelement.

In some embodiments, the drive mechanism may comprise a third driveelement, the third drive element constraining relative movement betweenthe first drive element and the second drive element when the drivemechanism is in the first position, wherein the third drive element isconfigured to engage the drug container or a portion of a housing of thedrug delivery device as the drive mechanism moves to the secondposition.

The third drive element may be configured to engage the drug containeror a portion of the housing of the drug delivery device at a releaseposition between the first position and the second position of the drivemechanism, and, as the drive mechanism moves from the release positionto the second position, the third drive element may be held stationaryrelative to the drug container or housing to release the first or seconddrive member from the third drive member. The third drive element may bepositioned between the first and second drive elements.

It is important that the first surface of the first drive element isdriven against the first surface of the second drive element reliablyand at the correct time, which is when the drug has been fully (oralmost fully) expelled from the drug container by the drive mechanism.There are inevitably some small variations in the dimensions of thecomponent parts of the device from one device to the next, no matterwhat manufacturing process is used. An advantage of configuring thethird element to engage the drug container directly is that it meansthat relatively few separate components are involved in determining whenthe first drive element is driven against the first surface of thesecond drive element, so the requirement for very fine dimensionaltolerances for each component is reduced, and the timing of the audibleindication can more closely match the end of drug delivery. In the firstposition of the drive mechanism, the first drive element and the seconddrive element may be constrained from relative rotation. In the secondposition of the drive mechanism the first drive element and the seconddrive element may be free to rotate relative to one another and,following or during relative rotation, may move in an axial directionrelative to one another.

The first drive element may comprise a first bearing surface, and thesecond drive element may comprise a second bearing surface engaging thefirst bearing surface in the first position of the drive mechanism,wherein rotation of the first drive element relative to the second driveelement moves the first bearing surface off the second bearing surface,allowing the first surface of the first drive element to strike thefirst surface of the second drive element, wherein in the first positionof the drive mechanism, the third drive element constrains relativerotation between the first drive element and the second drive element,and in the second position, the third drive element is moved axiallyrelative to the first and second drive elements to a position in whichthe third drive element does not constrain relative rotation between thefirst drive element and the second drive element.

The second drive element may comprise a first axially extendingprotrusion or slot that in the first position engages the third driveelement to prevent relative rotation between the second drive elementand the third drive element, and the first drive element may comprise anaxially extending slot or protrusion that in the first position engageswith the third drive element to prevent relative rotation between thethird drive element and the first drive element.

The third drive element may extend around at least a portion of thesecond drive element and the first drive element may extend around atleast a portion of the third drive element. The first and third driveelements may be generally tubular.

Alternatively, or in addition, the drug delivery device may comprise ahousing component coupled to or integral with the drug container, thehousing component constraining the first drive element from movingrelative to the second drive element in the first position of the drivemechanism. The drug delivery device may further comprise an externalhousing, wherein the drug container is configured to move through theexternal housing during operation of the device, and wherein the housingcomponent moves through the external housing with the drug container.The drug delivery device may comprise a hypodermic needle and thehousing component may be part of a needle insertion mechanism that movesthe drug container through the housing to insert the needle into aninjection site.

The drug delivery device may be an autoinjector.

In a second aspect, there is provided a drug delivery device comprising:

a housing;

a drug container, and

an powerpack assembly coupled to the drug container, the powerpackassembly comprising:

-   -   a stored energy source, the stored energy source configured to        release energy by expanding from a compressed state;    -   an insertion member engaging the stored energy source and        positioned between the stored energy source and the drug        container; and    -   a retaining means, in a first position the retaining means        engaging the stored energy source and the insertion member to        retain the stored energy source in a first compressed state;

wherein the retaining means and housing are configured such that theretaining means is moved by the housing to a second position onengagement of the powerpack assembly with the housing, the retainingmeans being disengaged from the stored energy source or the insertionmember in the second position;

the drug container and housing being configured such that the storedenergy source is retained in a second compressed state by the drugcontainer when the retaining means is moved to the second position, and

a triggering mechanism configured to release the stored energy sourcefrom the second compressed state when the autoinjector is to be used.

The housing may comprise a first cam surface configured to engage asecond cam surface on the retaining means. The retaining means andhousing may be configured such that the retaining means is rotated bythe housing to the second position on engagement of the powerpackassembly with the housing.

The stored energy source may be a compression spring or a gas spring,for example. The drug delivery device may further comprise a drivemechanism configured to drive a plunger through the drug container, thedrive mechanism comprising a second stored energy source, and a releasemechanism configured to control a sequence of release of the firststored energy source and the second stored energy source, wherein theretaining means forms a part of the release mechanism.

The drive mechanism may be configured to drive the drug containerthrough the housing in a longitudinal direction, and wherein theretaining means comprises a longitudinally extending retaining limb thatretains a drive element of the drive mechanism to the insertion memberto prevent a release of the second stored energy source. The retaininglimb may be configured to release the drive element from the insertionmember substantially at an end of travel of the drug container throughthe housing. The retaining means and housing may be configured such thatthe retaining means is rotated about a longitudinal axis by the housingto the second position. The retaining means may be held within thehousing and is inaccessible to a user during use. As used herein, theaxial direction, the longitudinal direction and the insertion directionare used to mean the same direction.

Prior to use of the device, the first stored energy source may bepositioned at least partially within the second stored energy source.The insertion element may comprise a first portion comprising a bearingsurface engaging the first stored energy source, and a second portionextending from the first portion, the second portion defining a recessin which the second stored energy source is received.

The insertion element may be assembled from two components to simplifymanufacture and assembly of the device.

The drive member may comprise a mechanism for providing an audibleindication in accordance with the first aspect of the invention.

The drug container may be retained by one or more latches on the housingor on an internal component coupled to the housing, to retain the storedenergy source in the second compressed state.

The triggering mechanism may comprise a movable skin sensor element,configured such that when the skin sensor element is pressed onto aninjection site, the skin sensor element moves to release the drive meansfrom the second deformed condition.

The drug delivery device may be an autoinjector.

In a third aspect of the invention there is provided a method forassembling a drug delivery device according to the second aspect of theinvention, comprising the steps of:

placing or forming a stored energy source in a powerpack assembly havinga powerpack housing;

retaining the stored energy source in the powerpack assembly in a firstcompressed condition using a retaining means coupled to the drive memberand the powerpack housing in a first position;

coupling the powerpack assembly to a drug container assembly, the drugcontainer assembly containing a drug to be dispensed by theautoinjector;

coupling the powerpack assembly and drug container assembly to an outerhousing; and

moving the retaining means to a second position to release the storedenergy source to second compressed condition, wherein the drug containerassembly and outer housing retain the stored energy source in the secondcompressed condition and wherein in the second compressed condition thestored energy source stores sufficient potential energy for needleinsertion and/or drug ejection when the autoinjector is to be used.

The step of moving the retaining means may be performed as a consequenceof the step of coupling to the outer housing.

The step of moving the retaining means may comprise rotation of theretaining means relative to the powerpack housing.

In a fourth aspect, there is provided a drug delivery device comprising:

a device housing;

a drug container within the housing and containing a drug, and a plungerpositioned within the drug container, the drug container having anoutlet for dispensing the drug; and

a powerpack assembly, the powerpack assembly comprising an insertionmember fixed to or abutting the drug container, a first stored energysource positioned between the insertion member and the device housing,and a second stored energy source positioned between the insertionmember and a drive member, wherein, in use, the drive member isconfigured to engage the plunger, wherein, in an initial position, thefirst stored energy source is located at least partially within thesecond stored energy source.

The insertion member may be driven by the first stored energy source tomove the drug container through the housing and the drive member may bedriven by the second stored energy source to move the plunger throughthe drug container.

The second stored energy source may be held within the insertion memberbefore operation of the device.

The insertion member may comprise a first portion comprising a firstbearing surface engaging the first stored energy source, and a secondportion extending from the first portion, the second portion defining arecess in which the second stored energy source is received. The firstor second portion of the insertion member may comprise a second bearingsurface engaging the drive member.

The drug delivery device may further comprise a retaining means, theretaining means coupled to the device housing, and extending within thefirst stored energy source and engaging the drive member or theinsertion member to prevent the drive member from disengaging from thesecond bearing surface. The device may be configured such that movementof the insertion member through the housing to an insertion positionreleases the drive member from the retaining means.

The first stored energy source may be configured to expand to releaseenergy to drive the insertion member within the device housing and thefirst stored energy source may be initially prevented from expanding bythe engagement of a portion of the device housing with the drugcontainer.

The drug delivery device may be an autoinjector.

In a fifth aspect of the invention, there is provided a drug deliverydevice, comprising:

a drug container;

an internal housing;

an insertion mechanism coupled to the drug container and configured tomove the drug container through the internal housing in an insertiondirection;

a skin sensor element, configured to contact an injection site in use;and

a skin sensor biasing element biasing the skin sensor in the insertiondirection;

wherein the skin sensor element is movable in a direction opposite tothe insertion direction from an initial position to a retracted positionto trigger the insertion mechanism;

wherein the internal housing includes a first latching element torestrain the skin sensor element from moving from the initial positionin the insertion direction, wherein the first latching element comprisesa latching surface configured to engage the skin sensor element and afirst camming surface; and

wherein either the drug container or the insertion mechanism includes asecond camming surface, wherein the second camming surface is configuredto engage the first camming surface to move the first latching elementas the drug container is moved through the internal housing in the axialdirection, thereby allowing the skin sensor element to move in theinsertion direction past the initial position to an extended position.In the extended position the skin sensor element covers the needle.

The first latching element may comprise a resilient cantilever arm,wherein the latching surface and the first camming surface are formed ata free end of the cantilever arm. The cantilever arm may be held intension by the skin sensor element and skin sensor biasing element whenthe skin sensor is in the initial position.

The internal housing may define a central bore through which the drugcontainer moves, and the first and second camming surfaces may beconfigured to move the latching element in a direction parallel to aperimeter of the bore. The first camming surface may be positionedinwardly of the latching surface. The first camming surfaceadvantageously extends non-parallel with the latching surface. Inwardlyin this context means further from an exterior surface of the device.

The skin sensor element may comprise at least a first aperture thataligns with a drug container latch on the internal housing when the skinsensor element is in the retracted position.

The skin sensor may be configured so as not to occlude a window in theinternal housing for viewing the drug container when in the initial orretracted position.

The drug delivery device may further comprise a second latching elementformed on the internal housing, the second latching element beingconfigured to prevent the skin sensor moving to the retracted positionafter it has been released from the first latching element. The secondlatching element may engage a second aperture or a protrusion on theskin sensor element.

In the retracted position the skin sensor element may abut the internalhousing to prevent further movement of the skin sensor element relativeto the internal housing in a direction opposite to the insertiondirection.

The drug delivery device may be an autoinjector.

In a sixth aspect of the invention there is provided a needle assemblycomprising:

a hypodermic needle;

a needle hub to which the needle is fixed at a first end;

a needle shield coupled to the needle hub and covering a second end ofthe needle; wherein the needle shield comprises a rigid body, the rigidbody providing a sterile barrier around at least a portion of theneedle; and

a compliant element within the rigid body, the compliant memberproviding a liquid tight seal around a second end of the needle,

wherein the rigid body is configured to provide an interference fit withthe needle hub and thereby provides a seal around the needle hub.

The rigid body may be formed from a moulded plastics material, such ashigh-density polyethylene or polypropylene.

The needle assembly may comprise at least one circumferential rib on aninterior surface of the rigid body or on an external surface of theneedle hub. Preferably, the needle assembly comprises at least twocircumferential ribs on the interior surface of the rigid body. Theradius of curvature of each rib at the contact point, prior to fittingof the rigid body to the needle hub is preferably less than 0.6 mm. Thecontact point of each rib is the point on the surface of the rib that isconfigured to first contact the needle hub when the rigid body is fittedto the needle hub.

The needle hub may be formed from a moulded plastics material, such ascyclic olefin polymer.

The needle hub may have a surface finish having a maximum distancebetween peak and trough of 2 μm or less. Preferably, a surface finish ofthe needle hub is 0.2 Ra or less. The needle hub may have a circularcylindrical outer surface to which the rigid body is coupled. Aninterior surface of the rigid body preferably has a surface finish of0.2 Ra or less. An interior surface of the rigid body may have a surfacefinish having a maximum distance between peak and trough of 2 μm orless.

The rigid body may comprise an external surface having at least oneprotrusion or recess. At least a portion of the rigid body may betransparent.

The compliant element may be fully enclosed, or may be only partiallyenclosed, by the rigid body and needle hub. The compliant element may beretained in the rigid body by at least one protrusion on the rigid body.

The needle assembly may further comprise at least one vent in thecompliant element or the rigid body for allowing air to escape from therigid body during insertion of the compliant element into the rigidbody. Alternatively, the rigid body may be moulded over the compliantelement, or the compliant element may be moulded inside the rigid body.

In a seventh aspect of the invention, there is provided an autoinjectoror syringe comprising a needle assembly in accordance with the sixthaspect.

In an eighth aspect of the invention, there is provided a method ofmanufacturing a needle assembly comprising:

fixing a first end of a needle to a needle hub; and

coupling a needle shield to the needle hub, the needle shield covering asecond end of the needle; wherein the needle shield comprises a rigidbody and a complaint element, wherein the rigid body is configured toprovide an interference fit with the needle hub and thereby provide aseal around the needle hub, the rigid body providing a sterile barrieraround at least a portion of the needle, the step of coupling includinginserting a second end of the needle into the compliant element suchthat the compliant element provides a liquid tight seal around thesecond end of the needle.

In a ninth aspect of the invention, there is provided a drug deliverydevice comprising:

a drug container assembly comprising a drug container containing a drug,a hypodermic needle coupled to the drug container and through which thedrug can be dispensed and a plunger within the drug container;

an internal housing, the drug container positioned within the internalhousing and movable through the internal housing;

a powerpack assembly comprising at least one stored energy source, thepowerpack assembly coupled to the drug container;

a lower housing fixed to the internal housing;

an upper housing fixed to the lower housing and enclosing the powerpackassembly;

a skin sensor element extending between the lower housing and theinternal housing and movable relative to the internal housing and thelower housing; and

a cap covering the skin sensor element and coupled to the lower housing.

The upper housing may be fixed to the lower housing using one or moremechanical fixings.

The device may be configured such that movement of the skin sensorelement relative to the internal housing from an initial position to aretracted position releases the stored energy source within thepowerpack assembly.

The internal housing may comprise retaining latches, which, when theskin sensor element is in the initial position, are engaged with thedrug container to retain the drug container in an initial position ofthe drug container to retain the stored energy source, and whereinmovement of the skin sensor element to the retracted position allows theretaining latches to disengage from the drug container, therebyreleasing the stored energy source. The internal housing may comprisefirst latching elements that restrain the skin sensor element frommovement out of the initial position. The first latching elements may beresilient arms that engage the skin sensor element at a free end.

The lower housing or internal housing may comprise second latchingelements that lock the skin sensor element in an extended position afterthe skin sensor has moved to the extended position.

The powerpack assembly may comprise first and second stored energysources, wherein the first stored energy source provides energy to movethe drug container from an initial position of the drug container to aninsertion position of the drug container, and wherein the second storedenergy source provides energy to move the plunger within the drugcontainer to dispense the drug. The powerpack assembly may be fixed tothe drug container. The stored energy sources may be compressionsprings.

The powerpack assembly may comprise a retaining means in accordance withthe second aspect of the invention. The powerpack may comprise a drivemechanism in accordance with the first aspect of the invention.

The internal housing may comprise a stopping surface configured toengage the drug container as the drug container moves to an insertionposition. The stopping surface may comprise one or more resilientcantilever beams that are deformed by the drug container as the drugcontainer moves to an insertion position.

The cap may directly or indirectly engage the skin sensor element, toprevent the skin sensor element from moving to a retracted position froman initial position.

The upper housing or lower housing may comprise an aperture to allow forviewing of the drug. The internal housing or the lower housing may betransparent and may be configured to engage the aperture in upperhousing.

The upper housing may comprise two major surfaces each including anaperture to allow for viewing of the drug, and two minor surfaces. Thefirst and second latching elements may be positioned adjacent a minorsurface of the upper housing.

The drug delivery device may be an autoinjector.

In a tenth aspect of the invention, there is provided a method ofassembling a drug delivery device according to the ninth aspect,comprising the steps of:

providing the powerpack assembly;

providing the drug container assembly;

providing a front end assembly comprising the internal housing, thelower housing and the skin sensor and the cap;

providing the upper housing;

coupling the powerpack assembly to the drug container assembly;

coupling the drug container assembly to the front end assembly; and

coupling the powerpack assembly, drug container assembly and front endassembly to the upper housing.

The step of coupling the powerpack assembly to the drug containerassembly may be performed before or after the step of coupling the drugcontainer assembly to the front end assembly. Similarly, the cap may becoupled to the other elements of the front end assembly at any point inthe method.

In an eleventh aspect of the invention, there is provided a drugdelivery device comprising:

a housing;

a drug container within the housing,

a powerpack assembly configured to move the drug container through thehousing in an axial direction from an initial position to an insertionposition,

wherein the housing includes a stopping surface configured to engage thedrug container when the drug container reaches the insertion position,wherein the stopping surface is provided on a least one resilient beamon the housing, the resilient beam being deflectable in the axialdirection.

The stopping surface may be provided on a pair of cantilever beams. Thedevice may comprise an outer housing and an internal housing, and thestopping surface is provided on the internal housing.

The drug container may comprise a hypodermic needle.

The drug delivery device may be an autoinjector.

In a twelfth aspect of the invention, there is provided a drug deliverydevice comprising:

a housing;

a drug container within the housing and containing a drug to bedispensed, the drug container having a first end defining a firstopening;

a plunger, positioned within the drug container, in contact with thedrug;

a first sealing element providing a first closure seal across the firstopening of the drug container;

a pusher initially located on an opposite side of the first closure sealto the plunger, wherein the pusher is operable to break the firstclosure seal and move the plunger within the drug container to dispensethe drug; and

an insertion mechanism configured to move the drug container through thehousing,

wherein, prior to use, the pusher and the insertion mechanism are heldout of contact with the first sealing element.

The sealing element may be laminated foil and may be welded or glued tothe drug container. The term “closure seal” as used herein in the claimsand description means a seal that prevents deterioration orcontamination of a drug in a container against foreseeable externalfactors in storage. A closure seal maintains the safety, identity,strength, quality, sterility and/or purity of a drug in a container incompliance with official, regulatory or established requirements.

The drug container may comprise a second opening through which the drugis dispensed and at least one side wall extending between the firstopening and the second opening, wherein the drive mechanism is engagedto the at least one sidewall.

The drug delivery device may be an autoinjector.

In a thirteenth aspect there is provided a drug delivery devicecomprising:

a housing;

a drug container within the housing and containing a drug to bedispensed, the drug container having a first end defining a firstopening;

a plunger, positioned within the drug container, in contact with thedrug;

a first sealing element providing a first closure seal across the firstopening of the drug container;

a pusher initially located on an opposite side of the first closure sealto the plunger, wherein the pusher is operable to break the firstclosure seal and move the plunger within the drug container to dispensethe drug; and

an insertion mechanism configured to move the drug container through thehousing prior to operation of the pusher to break the first closureseal,

wherein, no elements of the insertion mechanism and housing contact thefirst sealing element as the drug container is moved through thehousing.

The drug delivery device may be an autoinjector.

Features described in relation to one aspect of the invention mayequally be applied to any other aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an autoinjector in accordance with afirst embodiment of the invention, prior to use;

FIG. 2 is a first cross-section through the autoinjector of FIG. 1;

FIG. 3 is a second cross-section through the autoinjector of FIG. 1;

FIG. 4a is a perspective view of the drug container assembly;

FIG. 4b is a cross-section view of the drug container assembly;

FIG. 5 is a cross-section showing the needle shield and the needle hubof the drug container;

FIG. 6a is a first partial cross-section of the powerpack housing;

FIG. 6b is a second partial cross-section of the powerpack housing;

FIG. 7 is a top perspective view of the powerpack assembly;

FIG. 8 is a perspective view of the drive member in an initialconfiguration;

FIG. 9 is a perspective view of the drive member in a finalconfiguration, after drug delivery;

FIG. 10 is a perspective view of the skin sensor element;

FIG. 11 is a perspective view of the internal housing;

FIG. 12 is a perspective view of lower housing;

FIG. 13a is a side view of the device with the upper housing and capremoved, showing the skin sensor element in an initial position;

FIG. 13b is a side view of the device with the upper housing and capremoved, showing the skin sensor element in a retracted position;

FIG. 13c is a side view of the device with the upper housing and capremoved, showing the skin sensor element in a retracted position andwith the skin sensor latching element deflected by the powerpackassembly;

FIG. 13d is a side view of the device with the upper housing and capremoved, showing the skin sensor element and powerpack assembly in afinal position;

FIG. 14 is a perspective view of the cap;

FIG. 15 is a cross-section view of the front end of the device prior toremoval of the cap;

FIG. 16a-16g are cross-section views of the first embodiment,illustrating the sequence of operation;

FIG. 17 is a schematic diagram illustrating the assembly process of anautoinjector in accordance with the first embodiment of the invention;

FIG. 18 is a perspective view of an autoinjector in accordance with asecond embodiment of the invention, prior to use;

FIG. 19 is a first cross-section through the autoinjector of FIG. 18;

FIG. 20 is a second cross-section through the autoinjector of FIG. 18;

FIG. 21 is a perspective view of the drug container assembly of thesecond embodiment;

FIG. 22 is a perspective view of the powerpack housing of the secondembodiment;

FIG. 23 is a perspective view of a skin sensor element of the secondembodiment;

FIG. 24 is a perspective view of a chassis of the second embodiment;

FIGS. 25a to 25c are side views of the skin sensor element, chassis andpowerpack housing showing the sequence of movement of the skin sensorelement during use;

FIG. 26 is a perspective view of the lower housing of the secondembodiment;

FIG. 27 is a perspective of the cap of the second embodiment;

FIGS. 28a to 28e are cross-section views of the second embodiment,illustrating the sequence of operation;

FIG. 29 is a schematic diagram illustrating the assembly process of anautoinjector in accordance with the second embodiment of the invention;and

FIG. 30 illustrates the mechanism by which the powerpack is disengagedfrom the outer housing as it engages the chassis.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of an autoinjector 1 in accordance with afirst embodiment of the invention, before use. The autoinjectorcomprises an outer housing 20, having a viewing window 22 through whicha drug within the autoinjector can be inspected. A cap 30 is provided tocover the end of the device through which the needle passes duringoperation and to prevent inadvertent activation of the device. Theautoinjector is compact, being approximately 10 cm long and fits easilyin a user's hand.

FIG. 2 is a cross-sectional view through the autoinjector 1 of FIG. 1.FIG. 3 is a second cross-sectional view through the autoinjector of FIG.1, at 90 degrees to the cross-section of FIG. 2.

The autoinjector 1 shown in FIGS. 1, 2 and 3 comprises a drug containerassembly (shown in FIGS. 4a and 4b ), a powerpack assembly (shownpartially in FIGS. 6a, 6b and 7) including an end of delivery noisegenerating mechanism (shown in FIGS. 8 and 9), an internal housing(shown in FIG. 11), herein referred to as the chassis, a skin sensorassembly comprising a skin sensor element (shown in FIG. 10) and a skinsensor spring, a lower housing (shown in FIG. 12), an outer housing anda cap (shown in FIG. 14).

The drug container assembly 10 is held within the chassis 120 and inoperation moves through the chassis. The drug container assembly 10 isretained in an initial position by latches 122 on the chassis, whichengage protrusions 13 on the drug container and which are prevented fromreleasing the drug container by the skin sensor assembly. The skinsensor assembly comprises a skin sensor element 112 and a skin sensorspring 114. The skin sensor element is held by latching elements 124 onthe chassis 120 and urged away from the drug container assembly 10 bythe skin sensor spring 114, which is held between the chassis 120 andthe skin sensor element 112. The lower housing 140 engages the chassis120 by clipping to a window portion 130 of the chassis. Lugs 148 on thelower housing engage recesses 24 formed in the outer housing. The cap 30engages recesses 142 on the lower housing and covers the skin sensorelement 112.

The drug container assembly is shown alone in FIG. 4a . FIG. 4b is across-section view of FIG. 4a . The drug container assembly comprises adrug container 10 containing a drug to be delivered to a patient byinjection, with a hypodermic needle 12 fixed to a front end. The drugcontainer is formed from cyclic olefin, which has excellent drug contactproperties. The use of a plastic drug container has several advantagesover glass. A plastic container can be moulded with features that formpart of the automatic injection and drug delivery mechanism, asdescribed in relation to this embodiment below, and can be formed withmuch higher accuracy than glass, A plastic container can also withstandhigher impact forces and pressures allowing for the use of more powerfulsprings in the autoinjector mechanism and for a shorter, fatter drugcontainer.

A plunger 14 is provided within the drug container. Movement of theplunger 14 within the drug container 10 urges the drug out through theneedle 12. The plunger is designed to provide low friction with thewalls of the drug container and to minimise any station between theplunger and the drug container. The plunger is a cup seal type plunger,configured such that a component of the fluid pressure exerted by thedrug on the plunger as the plunger is moved through the drug containersis directed towards a sealing interface between the plunger and aninternal surface of the drug container. A plunger of this type isdescribed in GB2467904. A peripheral portion of the plunger 14 incontact with a wall of the drug container comprises a substantiallynon-elastomeric material. The internal surface of the front end of thedrug container 10 is shaped to match the shape of the front end of theplunger 14 to maximise the amount of drug that is pushed out of the drugcontainer during use.

A sealing foil 16 is provided at a back end of the drug container 10 toensure the drug is retained and maintained in a sterile and pristinecondition. The sealing foil 16 may be laminated foil including a layerof aluminium and may be welded or glued to a back end of the drugcontainer 10.

In this embodiment, the hypodermic needle 12 is glued into a needle hubportion 11 of the drug container 10. However, the drug container may bemoulded around the needle. The needle is covered by a needle shield 50that keeps the needle 12 sterile. As shown in FIG. 4b , the needleshield 50 comprises a rigid outer housing 52 that forms a seal with theneedle hub portion 11. A compliant element in the form of an elastomericplug 54 is provided within the needle shield into which the front end ofthe needle 12 is inserted. The elastomeric plug seals the needle andensures that no drug can escape from the needle prior to removal of theneedle shield. The rigid outer housing 52 of the needle shield may betransparent to allow for inspection of the needle during assembly of theautoinjector. The front end of the rigid outer housing 52 comprises abulb 56 configured to engage hooks 32 in the cap 30, as shown in FIG. 2a. This ensures that when the cap 30 is removed the needle shield isremoved with it.

The sealing of the needle shield to the needle hub 11 is shown in detailin FIG. 5, which is close-up view of a portion of FIG. 4b . The needlehub 11 is cylindrical where it surrounded by the needle shield. Therigid body 52 of the needle shield has a pair of ribs 57, 58 that extendaround the inner surface of the needle shield. The ribs have aninterference fit with the needle hub 11 to provide a seal that maintainsthe needle sterile. In this example, the hub has a diameter of 2.4 mmand a surface finish quality where the maximum distance between peak andtrough is no more than 2 μm. The needle hub may be formed from a mouldedplastics material, such as cyclic olefin polymer. The surface finish ofthe needle hub is specified to 0.2 Ra. The needle hub may have acircular cylindrical outer surface to which the rigid body is coupled.An interior surface of the rigid body is specified to have a surfacefinish of 0.2 Ra or less. An interior surface of the rigid body may havea surface finish having a maximum distance between peak and trough of 2μm or less. The ribs have a nominal sealing diameter of 2.2 mm. There istherefore a nominal diametrical interference between the needle hub 11and the needle shield 50 of 0.2 mm.

The rigid body of the needle shield is formed from polyethylene and hasthe same surface finish as the needle hub. The ribs 57, 58 are spacedfrom one another by 3 mm. In order to provide the greatest contactpressure between the ribs and the needle hub, combined with the lowestforce, and so the tightest seal with the lowest removal force, thecontact area between the ribs and the needle hub should be a small aspossible. However, the contact area is limited by the manufacturingprocess for the needle shield and the materials used. In this example,the radius of curvature of each rib at the contact point, prior tofitting of the rigid body to the needle hub is preferably less than 0.6mm. The contact point of each rib is the point on the surface of the ribthat is configured to first contact the needle hub when the rigid bodyis fitted to the needle hub. However, the final contact radius may belarger than this, particularly if the plastic is deformed by theinterference.

The autoinjector shown in FIGS. 1 to 3 also comprises an automaticmechanism for inserting the needle into an injection site and forejecting the drug through the needle into the injection site. Theautomatic mechanism is referred to herein as the powerpack assembly. Thepowerpack assembly comprises stored energy sources, in the form ofcompressed springs 61, 62. When the first spring 61, referred to as theinsertion spring, is released it moves the drug container 10 through thehousing of the autoinjector to insert the needle 12 into an injectionsite. The second spring 62, referred to as the delivery spring, is thenreleased to move the plunger 14 through the drug container 10 to injectthe drug. The springs 61, 62 and the mechanism for controlling asequence of release of the springs within the powerpack assembly arepositioned rearward of the drug container.

The powerpack comprises a powerpack housing 64 that is coupled to thedrug container 10. The powerpack housing of this embodiment comprisestwo parts, a lower powerpack housing 65 and an upper powerpack housing66. The powerpack housing is in two parts to simplify the assembly ofthe autoinjector, but, in use, the two parts are fixed to each other andact as a single component. The lower powerpack housing 65 is clipped tothe drug container 10. The lower powerpack housing 65 engages recesses17 on the drug container. The insertion spring 61, shown in FIGS. 2 and3 in a compressed condition prior to use of the autoinjector, ispositioned between the upper powerpack housing 66 and a retaining means100. The retaining means 100 is coupled to the upper powerpack housing66 to retain the insertion spring 61 in a first compressed condition, asis explained with reference to FIG. 7.

The delivery spring 62 is positioned between the upper powerpack housing66 and a multiple component drive member 70. When released, the deliveryspring 62 drives the drive member 70 forward relative to the powerpackhousing 64 and so drives the plunger 14 through the drug container 10 toeject the drug, as is described in detail below.

Before use of the autoinjector, the delivery spring 62 is positionedaround the insertion spring 61. A two-spring mechanism, nested in thisway has advantages. Firstly, by nesting one spring within the other, thelength of the autoinjector is minimised. Secondly, the delivery springcan be made larger than the insertion spring. The force required toeject the drug through the needle is typically much greater than theforce required to insert the needle into an injection site. The use of asmaller spring for needle insertion is therefore beneficial. The rearend of the powerpack assembly is shown in detail in FIGS. 6a and 6b .FIG. 6a is a first cross-section through the powerpack assembly andshows the insertion spring seated on a first ledge 67 formed on theupper powerpack housing 66. FIG. 6b is a second cross-section throughthe powerpack assembly, at ninety degrees to the cross-section of FIG.6a , and shows the drive member 70 retained by a second ledge 69 formedon the upper powerpack housing.

The powerpack assembly is assembled as a separate component before it iscoupled to the drug container and the rest of the autoinjector. In orderto retain the insertion spring and delivery spring in a compressedcondition, the powerpack housing engages the retaining means 100. Theretaining means comprises a head portion 106 and a shaft portion 108that extends from the head portion within the powerpack housing 64 andthe drive member 70. The shaft portion 108 ensures that the drive member70, and in particular lobes 86 on the second drive element 80, cannotdisengage from the ledge 69 on the powerpack housing until the drivemember is moved clear of the shaft portion 108.

FIG. 7 is a partial, perspective top view of the powerpack assembly,showing the retaining means 100 engaging the upper powerpack housing 66.The insertion spring 61 urges the powerpack housing away from theretaining means 100 but it is retained by the engagement of surfaces 102on the retaining means under shelves 68 formed on the upper powerpackhousing. The powerpack housing is released from the retaining means 100by relative rotation between the powerpack housing and the retainingmeans. In particular, cam surfaces 104 are formed on the retaining meansso that when the powerpack assembly is inserted into the outer housing,cam surfaces or protrusions 25 within the outer housing engage the camsurfaces on the retaining means and force the retaining means to rotate.The powerpack housing is prevented from rotating relative to the outerhousing by engagement of the powerpack housing with the chassis andengagement of the chassis with the outer housing. The rotation of theretaining means 100 moves surfaces 102 out of engagement with shelves 68so that the powerpack housing is disengaged from the retaining means.

Once the powerpack housing has been released from the retaining means100 it is prevented from fully expanding by the engagement of the outerhousing 20 with the lower housing 140, the engagement of the lowerhousing 140 with the chassis 120, the engagement of the chassis 120 withthe drug container 10 and the engagement of the drug container 10 to thepowerpack housing 64. The outer housing 20 is configured to engage thelower housing 140 as it drives the retaining means 100 out of engagementwith the powerpack housing by rotating the retaining means.

As described, the insertion spring 61 engages the ledge 67 on the upperpowerpack housing 66 to drive the powerpack housing and drug containerassembly forward through the chassis as it expands. The drive spring 62engages the powerpack housing 64 and the drive member 70 to drive thedrive member and plunger through the drug container. The drive member 70comprises three components. Specifically, the drive spring engages aspring bearing surface 72 on a first drive element 71. The first driveelement 71 is coupled to a second drive element 80 and a third driveelement 90. The multiple element drive member 70 is shown in FIGS. 8 and9.

The drive member 70 is shown in an initial configuration in FIG. 8,prior to delivery of the drug from the drug container. The first driveelement 71 is essentially a circular cylindrical tube, within which asecond drive element 80 is located. A first striking surface 75 on thefirst drive element is held apart from a first striking surface 85 onthe second drive element by the engagement of the first drive elementwith a tooth 84 that extends from the first striking surface on thesecond drive element towards the first drive element. The second driveelement comprises a foil contact surface 82 configured to contact andpierce the sealing foil 16 on the drug container 10. The foil contactsurface 82 comprises a plurality of serrations to assist in piercing thefoil seal. The second drive element 80 extends from the first strikingsurface 85, through the first drive element.

The second drive element is formed from a moulded plastics material andis divided at its rear end into a pair of flexible legs 87, at the rearend of each of which a lobe 86 is formed for engagement with thepowerpack housing. A bore 88 is defined between the legs, into which theshaft portion 108 of the retaining means is received. The shaft portionof the retaining means prevents the legs 87 from deflecting inwardly todisengage from the ledge 69 on the upper powerpack housing.

The first drive element 71 comprises a cut-out 73 that is dimensioned toreceive tooth 84 of the second drive element so that the first strikingsurface 75 on the first drive element and contact the first strikingsurface 85 on the second drive element. In order for tooth 84 to bereceived in the cut-out 73 the first drive element must be rotatedrelative to the second drive element. However, in an initial position,this is prevented by the third drive element 90. The third drive element90 engages both the first drive element and the second drive element inthe initial position. The third drive element in this embodiment isgenerally tubular and is positioned between the first drive element andthe second drive element. A protrusion 92 on the third drive elementengages a slot 74 formed in the first drive element to prevent relativerotation of the first drive element and the third drive element. Theslot is dimensioned to allow axial movement i.e. movement in thedirection of travel of the drive member on expansion of the drivespring, between the first drive element and the third drive element. Acut-out 94 in the third drive element engages the tooth 84 on the seconddrive element to prevent relative rotation between the second driveelement and the third drive element. However, the third drive element isfree to move axially relative to the second drive element.

As the drive member reaches the end of its forward travel through thedrug container, the protrusion 92 on the third drive element engages arear surface of the drug container 10. The third drive element is thusheld by the drug container as the first and second drive elementscontinue to move forwards under the influence of the drive spring 62.When the cut-out 94 in the third drive element is disengaged from thetooth 84 as a result of the this relative axial movement between thethird drive element and the second drive element, the first driveelement 71 is free to rotate relative to the second drive element 80.Tooth 84 engages the first drive element on an angled surface 76 so thatthe action of the drive spring on the first drive element 71 forces itto rotate relative to the second drive element. When the tooth 84 isfree to enter cut-out 73, the first drive element moves forward rapidlyrelative the second drive element as there is no significant resistanceto that forward movement. The first striking surface on the first driveelement then strikes the first striking surface on the second driveelement at high speed, creating an audible single indicative of thedrive member reaching the end of its travel. The final position is shownin FIG. 9.

A principle of operation of this “end-of-delivery” indication is to usea two-part drive member in which the two parts move together until at ornear to the end of travel of the drive member, whereupon the two partsare free to move relative to one another under the action of a storedenergy source to create an audible signal. It is advantageous to use thesame energy source as is used to drive the drive member through the drugcontainer. However, it should be clear that there are several optionsfor the mechanism for locking and releasing the two parts of the drivemember, which in the embodiment of FIGS. 8 and 9 is realised using thethird drive member. For example, features within the powerpack housingmight be provided to force the first drive element to rotate relative tothe second drive element when the first drive element reaches aparticular position within the powerpack housing.

A skin sensor assembly is provided forward of the drug container, whichcovers the needle both before and after use and which allows theautoinjector to be activated simply by removing a cap and pressing theautoinjector against an injection site.

The skin sensor assembly comprises a skin sensor element 112, shown inFIG. 10, and skin sensor spring 114 that is held between the skin sensorelement and the chassis. This can be seen clearly in FIG. 3. Inoperation, the skin sensor element interacts with the chassis 120 shownin FIG. 11 and the lower housing 140 shown in FIG. 12.

FIG. 11 is a perspective view of the chassis 120. The chassis is formedfrom a transparent plastic material and includes two window portions120, which align with the windows 22 formed in the outer housing 20. Thelower housing 140 clips to the chassis around the window portion 130, asshown in FIG. 13a . Latches 122 are formed so that they can be flexedoutward, out of engagement with the drug container 10. The chassis has afront end 132 of reduced diameter, which prevents the drug containerfrom travelling beyond an insertion position. A bearing surface 133 isprovided against which the skin sensor spring 114 sits.

The chassis 120 also includes flexible arms 121 formed below the windowportions 130. The flexible arms 121 each comprise a bulb 123 at theirfree end that abuts a rear end of the skin sensor element 112. The bulb123 (in combination with the cap and/or upper housing) prevents the skinsensor element being moved rearward to a position in which the latches122 can release the drug container 10, as described with reference toFIG. 15. The chassis also includes latching elements 124. Each latchingelements 124 comprises a flexible arm 125 extending from the body of thechassis towards a front end of the device, and a hook 126 and cam head128 on the end of the flexible arm. The hook 126 is configured to engagethe skin sensor element 112. The cam head 128 is positioned inward ofthe hook and is configured to engage the powerpack housing 64. Inward inthis context is relative to the outer housing. The latching elements 124on the chassis do not extend inwardly of the surrounding portion of thechassis in order to engage the powerpack or skin sensor element. This isadvantageous from a moulding perspective.

FIG. 12 is a perspective view of the lower housing 140. The lowerhousing is secured to the chassis by the clipping of portion 146 aroundwindow portion 130 of the chassis. The lower housing 140 includes a pairof second latching elements 144 that, in the initial position arereceived in openings 115 of the skin sensor element 112. The lowerhousing includes recesses 142 for engagement with the cap 30. Surface145 acts to limit movement of the skin sensor beyond a fully extendedposition, as will be described. The lower housing also includes slots141, into which flexible arms 121 of the chassis are received. Lugs 148on the lower housing engage recesses 24 formed in the outer housing. Inan initial position, prior to use, and as shown in FIGS. 2 and 3, theskin sensor element 112 is urged away from the chassis by the skinsensor spring 114. It is retained to the chassis by engagement ofsurfaces 116 with latching elements 124. The second latching elements144 on the lower housing, in the initial position, are received inopenings 115 of the skin sensor element 112.

FIGS. 13a-13d show the sequence of operation of the skin sensorassembly, and are side views of the device with the outer housing andcap removed. FIG. 13a shows the device with the cap removed but prior touse. The skin sensor element 112 is retained against the action of theskin sensor spring by the latching element 124. Specifically hook 126 onthe latching element 124 engages surface 114 on the skin sensor element.

FIG. 13b shows the skin sensor element 112 pushed back, as it would beif the skin sensor element were pressed against an injection site. Inthis position, the hook 126 is clear of the surface 116. The secondlatching elements 144 are still received in opening 115 of the skinsensor element. However, the wider portions of opening 115 are nowaligned with the position of latches 122 on the chassis. In the positionshown in FIG. 13b , the latches 122 no longer retain the drug container10, as they can be pushed outwards into the opening 115 in the skinsensor element. Accordingly, the drug container is free to move forwardand the insertion spring 61 expands to move the powerpack assembly anddrug container to an insertion position, as shown in FIG. 13 c.

In FIG. 13c the drug container is in an insertion position, and needle12 is clearly extending beyond the skin sensor element 112. In thisposition, the powerpack assembly has moved forward so that protrusions63 on the powerpack housing 64, only an upper end of which can be seenin FIG. 2, have pushed against cam head 128 and so have deformed arm124. The deformation of arm 124 moves the hook 126 out of the path ofsurface 116 when it moves forward.

When the device is removed from the injection site, the skin sensorspring urges the skin sensor element forward. As the arm is deformed,the surface 116 can move past hook 126. The skin sensor element can thenmove to a fully extended position as shown in FIG. 13d . In thisposition the skin sensor element covers the needle again. The skinsensor element is retained to the chassis and prevented from furtherforward movement by the surface 117 on the skin sensor element abuttingthe surface 145 on the lower housing. The second latching elements 144engage with aperture 118 in the skin sensor element 112 to prevent theskin sensor element from being moved back against the skin sensorspring. The second latching elements can ride over sloped surface 119 onthe skin sensor element as it moves to its fully extended position tosnap into the aperture 118, whereupon the skin sensor element is lockedin a fully extended position.

The latching mechanism for the skin sensor and for retaining andreleasing the drug container is all positioned on two opposite sides ofthe device. This allows the window 22 to remain unobscured throughoutoperation of the device. This allows the drug to be easily inspectedbefore use and for the progress of the drug delivery to be observedthrough the window 22.

The device shown in FIGS. 1 to 13 includes a mechanism to preventactivation prior to removal of the cap. FIG. 14 is a perspective view ofthe cap 30. The cap is formed from a moulded plastics material andcomprises protrusions 34 that are configured to engage recesses 142 onthe lower body, as shown in FIG. 2. The upstanding central tubecomprises the hooks 32 shown in FIG. 2, for retaining the needle shield.The cap also includes tongues 36 that extend within a space between theouter housing and the chassis when the cap is fitted to the device, asshown in FIG. 3.

FIG. 15 is a detail view of the front end of the device as shown in FIG.3. It can be seen that the tongues 36 on the cap are adjacent flexiblearms 121 formed on the chassis, and shown more clearly in FIG. 11. Theflexible arms 121 comprise a bulb 123 that abuts a rear end of the skinsensor element 112. The bulb 123 prevents the skin sensor element beingmoved rearward to a position in which the latches 122 can release thedrug container 10. So, when the cap is engaged to the lower housing 140,the device cannot be activated.

When the cap is removed, the arms 121 can be pushed outwardly by theskin sensor element into the space vacated by the tongues 36, as it theskin sensor is moved rearward. The skin sensor element and bulbs 123 areshaped to allow this to happen smoothly. The lower housing includesapertures 141 into which the arms 123 can deflect.

FIGS. 16a to 16g illustrate the sequence of operation of the device ofthe first embodiment. FIGS. 16a to 16g are cross-section views, similarto FIG. 2, but with the cap removed.

FIG. 16a shows the device immediately after cap removal, but prior tothe pressing of the skin sensor element against an injection site. Itcan be seen that the needle shield assembly has been removed togetherwith the cap.

FIG. 16b shows the device with the skin sensor element pushed back.Second latching elements 144 on the lower housing prevent the skinsensor from moving further back. In this position, the latches 122 onthe chassis are free to bend out into the windows 115, but have not yetdone so.

FIG. 16c shows the drug container 10 and powerpack housing 64 moved toan insertion position by the expansion of insertion spring 61. In thisposition, the needle 12 is inserted into the injection site. The seconddrive element 80 is just clear of the shaft portion 108 of the retainingmeans 100. This means that legs 87 can be squeezed together to disengagefrom the lugs 86 from surface 69 on the powerpack housing 64. Theprotrusions 63 on the powerpack housing has deflected the latching arms124 so that the skin sensor element 112 is free to move forward to afully extended position once it is removed from the injection site.

FIG. 16d shows the drive member disengaged from the powerpack housingand at the point of first contact of the drive member with the sealingfoil. The drive spring is expanding to urge the drive member forward.

FIG. 16e shows the drive spring further expanded and the drive memberfurther forward. The foil has been ruptured and the plunger has beenmoved through the drug container and almost all the drug has beenejected. At this point, the third drive element has engaged the rear endof the drug container and so moved back relative to the second driveelement. In this position, the drive element is no longer engaged to thesecond drive element, and the second drive element is able to rotaterelative to the first drive element, as described with reference toFIGS. 8 and 9.

FIG. 16f shows the first drive element driven forward onto the seconddrive element, with the second drive element rotated, to provide anaudible indication of the end of drug delivery. The plunger is in afully forward position, with the intended volume of drug ejected. Atthis point, the user can remove the device from the injection site.

FIG. 16g shows the device after it has been removed from the injectionsite, with the skin sensor element in a fully extended position, lockedand covering the needle. As described with reference to FIG. 13d , theskin sensor element is retained to the chassis and prevented fromfurther forward movement by surface 117 on the skin sensor elementabutting the surface 145 on the lower housing. The second latchingelements 144 engage with aperture 118 in the skin sensor element 112 toprevent the skin sensor element from being moved back against the skinsensor spring.

It can be seen from FIG. 2 and FIGS. 16a-c , that the drive member 70and all of the other components of the device are held apart from thesealing foil 16 until the time at which the sealing foil is ruptured.Prior to use, the drive member 70 is held a predetermined distance fromthe sealing foil 16. The powerpack housing 64 is fixed to the sides ofthe drug container and does not contact the sealing foil. During theneedle insertion stage of operation, the sealing foil 16 remainsuntouched. This arrangement ensures that the sealing foil can be testedbefore the drug container is assembled to the rest of the autoinjector,and the sealing foil then remains untouched until the point of drugdelivery. This reduces the possibility of contamination or loss of drugbefore delivery.

FIG. 17 is a schematic diagram illustrating the sequence of assembly ofan autoinjector of the first embodiment. In step 150, the drug containerassembly 10, including the needle 12 and needle shield 50 is filled withdose of drug and a plunger 14, and then sealed by a sealing foil 16.This is carried out in a sterile environment. Independently, in step152, the powerpack assembly is assembled, with the retaining meansholding the drive and insertion springs in a compressed state. In step154 the filled drug container assembly in then fitted to the powerpackassembly, the lower powerpack housing clipping to the drug container 10.In step 156, the front end of the device, including the chassis, skinsensor element, skin sensor spring, and lower housing are assembled. Thecap is typically coupled to the front end assembly at this stage, butthis is shown as a separate step 157. In step 158 the front end assemblyis coupled to the drug container assembly and powerpack assembly. Thedrug container assembly is retained by latching arms on the chassis. Instep 160, the outer housing is placed over the powerpack assembly andengages with the lower housing 140. The cam surfaces 25 on the outerhousing 20 engage the retaining means 100 and force the retaining meansto rotate out of engagement with the powerpack housing 64 just beforethe lugs 148 on the lower housing engage recesses 24 formed in the outerhousing. The insertion spring 61 is allowed to expand a small amount asthe powerpack housing disengages from the retaining means, but it isheld in a second compressed state by the action of latches 122 on thechassis engaging the drug container 10. In the second compressed state,the insertion spring still stores enough energy to insert the needle 12into an injection site by pushing the drug container to the insertionposition.

The cap 30 is typically assembled to the lower housing 140 duringassembly of the front end assembly, but may be added after the powerpackand front assembly are joined or after the outer housing has been fittedto the lower housing. These options are illustrated in FIG. 17 as step157.

The autoinjector is fully assembled and ready for use at step 162. Thisproduction sequence has the advantage that the powerpack assembly can beproduced independently of the other components and transported andstored separately. Steps 156, 157, 158 and 160 are very simple andeasily automated.

The first described embodiment also has the advantage that differentlength and shaped outer housing can be used for different drugs with thesame powerpack assembly. The features 25 used to rotate the retainingmeans out of engagement with the powerpack housing 64 do not need to bemanufactured with the same tight tolerances on dimensions that the shaftportion 108 of the retaining means requires. It is therefore a simplematter to provide different outer housings to provide a distinctiveappearance for devices for particular drugs or for devices associatedwith particular brands. Users can then quickly recognise if they havethe appropriate device. Different outer housing may also be provided tosuit different user groups that may have different specific requirementse.g. they may have limited manual dexterity.

FIG. 18 is a perspective view of an autoinjector 201 in accordance witha second embodiment of the invention, before use. The autoinjector 201comprises an outer housing 220, having a viewing window 222 throughwhich a drug within the autoinjector can be inspected. A cap 230 isprovided to cover the needle insertion end of the device and to preventinadvertent activation of the device. The autoinjector is compact, beingapproximately 10 cm long and fits easily in a user's hand.

FIG. 19 is a cross-sectional view through the autoinjector 201 of FIG.19. FIG. 20 is a second cross-sectional view through the autoinjector ofFIG. 19, at 90 degrees to the cross-section of FIG. 19.

The autoinjector 201 shown in FIGS. 18, 19 and 20 comprises a drugcontainer assembly (shown in FIG. 21), a powerpack assembly including apowerpack housing 264 (as shown in FIG. 27), a drive member 270 andinsertion and drive springs 260, 262, an internal housing (shown in FIG.23), herein referred to as the chassis, a skin sensor assemblycomprising a skin sensor element (shown in FIG. 22) and a skin sensorspring, a lower housing (shown in FIG. 26), an outer housing and a cap(shown in FIG. 25). The drug container assembly 210 is held within thechassis 320 and in operation moves through the chassis. The drugcontainer assembly 210 is retained in an initial position by latches 322on the chassis, which engage protrusions 213 on the cradle 215 thatsurrounds the drug container 211. The latches 322 are prevented fromreleasing the cradle by the skin sensor assembly. The skin sensorassembly comprises a skin sensor element 312 and a skin sensor spring314. The skin sensor element is held by latching elements 324 on thechassis 320 and urged away from the drug container assembly 210 by theskin sensor spring 314, which is held between the chassis 320 and theskin sensor element 312. The lower housing 340 engages the chassis 320by clipping to a T-shaped protrusion 328 on the chassis. Window portions348 on the lower housing engage window 222 formed in the outer housing.The cap 230 engages the channel 342 on the lower housing and covers theskin sensor element 312.

FIG. 21 is a perspective view of the drug container assembly shown inFIGS. 19 and 20. The drug container assembly comprises a drug container211 and cradle element in which the drug container 211 is held. Thecradle and drug container may be formed as separate components or may beco-moulded together. The drug container 211 contains a drug to bedelivered to a patient by injection, with a hypodermic needle 212 fixedto a front end. As in the first embodiment, the drug container is formedfrom cyclic olefin, which has excellent drug contact properties. Thecradle may be formed of a different material and advantageously isformed from a mouldable plastic. Clipping features 213 and 219 areformed on the cradle 215.

A plunger 214 is provided within the drug container. Movement of theplunger 214 within the drug container 211 urges the drug out through theneedle 212. The plunger is of the same type as described with referenceto the first embodiment and is designed to provide low friction with thewalls of the drug container and to minimise any stiction between theplunger and the drug container. The internal surface of the front end ofthe drug container 211 is again shaped to match the shape of the frontend of the plunger 214 to maximise the amount of drug that is pushed outof the drug container during use.

A sealing foil 216 is provided at a back end of the drug container 211to ensure the drug is retained and maintained in a sterile and pristinecondition. The sealing foil 216 may be laminated foil including a layerof aluminium and may be welded to a back end of the drug container 211.

As in the first embodiment, the hypodermic needle 212 is glued into aneedle hub portion 217 of the drug container 211. However, the drugcontainer may be moulded around the needle. The needle is covered by aneedle shield 250 that keeps the needle 212 sterile. As described in thefirst embodiment, the needle shield 250 comprises a rigid outer housing252 that forms a seal with the needle hub portion 217. An elastomericplug 254 is provided within the needle shield into which the front endof the needle 212 is inserted. The elastomeric plug seals the needle andensures that no drug can escape from the needle prior to removal of theneedle shield. The rigid outer housing 252 of the needle shield may betransparent to allow for inspection of the needle during assembly of theautoinjector. The front end of the needle shield outer housing 252comprises a bulb 256 to engage hooks 232 in the cap 230, as shown inFIG. 19. This ensures that when the cap 230 is removed the needle shieldis removed with it.

The sealing of the needle shield to the needle hub is achieved using aninterference fit in the same manner as described for the firstembodiment and shown in FIG. 5.

As in the first embodiment, the autoinjector shown in FIGS. 18 to 20comprises an automatic mechanism for inserting the needle into aninjection site and for ejecting the drug through the needle into theinjection site. The automatic mechanism is referred to herein as thepowerpack assembly. The powerpack assembly comprises stored energysources, in the form of compressed springs 260, 262. When the firstspring 260, referred to as the insertion spring, is released it movesthe drug container assembly 210 through the housing of the autoinjectorto insert the needle 212 into an injection site. The second spring 262,referred to as the delivery spring, is then released to move the plunger214 through the drug container 211 to inject the drug. The springs 260,262 and the mechanism for controlling a sequence of release of thesprings within the powerpack assembly are positioned rearward of thedrug container assembly.

The powerpack comprises a powerpack housing 264, shown in FIG. 22, thatis coupled to the drug container assembly 210. The powerpack housing 264has arms 265 that clip to the features 219 on the cradle 215. Theinsertion spring 260, shown in FIGS. 19 and 20 in a compressed conditionprior to use of the autoinjector, is positioned between the powerpackhousing 264 and the outer housing 220. When the drug container assemblyis released from the latches 322 on the chassis, the drug containerassembly is free to move forward through the chassis to an insertionposition, pushed by the expansion of the insertion spring 260, as willbe described.

The drive spring 262 is positioned between the powerpack housing 264 anda drive member 270. In an initial position, the drive spring isprevented from expanding by the engagement of protrusions 272 on thedrive member 270 with surface 267 on the powerpack housing.

The drive member 270 comprises a front end surface 276 that has aserrations to aid rupture of the sealing foil 216 and which in useengages with the plunger, as will be described. The drive member 270also has resilient legs 274 that are pressed outwardly by a lockingsurface 226 that is part of (or rigidly fixed to) the main housing 20 sothat protrusions 272 engage with the powerpack housing and are preventedfrom disengagement with the locking surface 226. In this way the drivespring 262 is locked in a compressed state, and moves with the powerpackhousing 264, until the protrusions 272 can be released from the surface267.

When the powerpack housing has traveled to an insertion position, thedrive member has traveled beyond the locking surface 226. At this point,because the locking surface is no longer between the legs 274, the legs274 can be squeezed together allowing the drive member to disengage fromthe surface 267 on the powerpack housing. The drive member can then bemoved forward by the drive spring 262 to rupture the sealing foil 216and push the plunger 214 through the drug container 211 to dispense thedrug through the needle 212.

As in the first embodiment, in the second embodiment a skin sensorassembly is provided forward of the drug container, which covers theneedle both before and after use and which allows the autoinjector to beactivated simply by removing a cap and pressing the autoinjector againstan injection site.

The skin sensor assembly comprises a skin sensor element 312 and a skinsensor spring 314. The skin sensor spring 314 is held between the skinsensor element and the chassis. This can be seen clearly in FIG. 19. Inoperation, the skin sensor element interacts with the chassis 320.

FIG. 23 is a perspective view of the skin sensor element of the secondembodiment. The skin sensor element comprises a front surface 313 whichcontacts the injection site in use, and which has an aperture throughwhich the needle passes during insertion of the needle. Apertures 315are provided so that when the skin senor element is in a retractedposition they align with the latches 322 on the chassis, allowing thelatches to deflect outwardly out of engagement with features 213,releasing the drug container. Hooks 316 are provided to engage thechassis in an initial position, retaining the skin sensor elementagainst the force applied by the skin sensor spring. Surfaces 317 areprovided to abut the chassis and prevent retraction of the chassis whenthe skin sensor element is in a fully extended position. Bracing arms318 provide mechanical rigidity.

FIG. 24 is a perspective view of a chassis of the second embodiment. Thechassis is formed from a plastics material. The chassis is againessential tubular with a central bore through which the drug containerassembly can move axially. The chassis has a front end 332 of reduceddiameter beyond which the drug container assembly cannot travel. At thefront end, the chassis includes a pair of cantilever arms 334 extendingradially inward. The drug container assembly contacts and deflects thecantilever arms in the insertion direction, also referred to as theaxial direction herein, as it moves to an insertion position. Thedeflection of the cantilever arms decelerates the drug containerassembly as it reaches the insertion position, reducing force applied tothe injection site through the skin sensor spring and skin sensor fromthe chassis. The cantilever arms 334 are constructed to extend rearwardfrom their fixed end to their free end so that they can deflect beforebeing level with the rest of the front end of the chassis.

The chassis comprises latching elements 324 that engage hooks 316 on theskin sensor element. The latching elements 324 are resilient arms thatextend rearward from their fixed end but at an angle offset from theaxial direction. The latching elements can be deflected by cammingfeatures 269 on the powerpack assembly to allow the hooks 316 to pass asthe skin sensor moves to an extended position. The chassis compriseslocking arms 326, which are resilient arms that extend forward fromtheir fixed end. The locking arms can flex to allow the skin sensorelement to pass when the skin sensor moves from a retracted position toan extended position, but are configured to prevent the surfaces 317from passing back over the locking arms 326 once the skin senor hasreached the fully extended position. FIGS. 25a-25c show the sequence ofoperation of the skin sensor assembly, and are side views of the devicewith the outer housing and cap removed. FIG. 25a shows the device priorto use. The skin sensor element 312 is retained against the action ofthe skin sensor spring by the latching element 324. Specifically hook316 on the skin sensor element engages the latching element 324.

FIG. 25b shows the skin sensor element 312 pushed back, as it would beif the skin sensor element were pressed against an injection site, andthe powerpack moved forward. In this position, the hook 316 is clear ofthe surface latching element 324. The apertures 315 are now aligned withthe position of latches 322 on the chassis. In the position shown inFIG. 25b , the latches 322 no longer retain the drug container assembly210, as they can be pushed outwards into the apertures 315 in the skinsensor element. Accordingly, the drug container 311 has moved forwardand the insertion spring 261 expanded to move the powerpack assembly anddrug container to an insertion position.

As the powerpack assembly moves forward to the insertion position,camming ridge 269 engages the latching elements 324 to deflect thelatching elements so that they extend in an axial direction, as shown.

When the device is removed from the injection site, the skin sensorspring 314 urges the skin sensor element 312 forward. As the latchingarms 324 are deflected, the hooks 316 can pass the latching elements 324as the skin sensor element moves forward. The skin sensor element 312can then move to a fully extended position as shown in FIG. 25c . Inthis position, the skin sensor element covers the needle again. The skinsensor element is retained to the chassis and prevented from furtherforward movement by the engagement of bracing arms 318 with a portion ofthe lower housing 340 (not shown in FIG. 25c ). The locking arms 326flex to allow the skin sensor element to pass when the skin sensor movesfrom a retracted position to an extended position, but surfaces 317 thenengage the locking arms 326 if the skin sensor element is pushed backtowards a retracted position, locking the skin sensor element in theextended position.

FIG. 26 is a perspective view of the lower housing of the secondembodiment. The lower housing 340 is formed from a transparent plasticsmaterial and includes window portions 348. The lower housing fits overthe skin sensor and chassis but partially within the outer housing.Window portions 348 have raised outer rims that and engage windows 222formed in the outer housing. The lower housing 340 engages the chassis320 by apertures 344 receiving T-shaped protrusions 328 on the chassisChannel 342 on the lower housing is provided to engage the cap 330.

FIG. 27 is a perspective of the cap of the second embodiment. The cap230 comprises a central cylindrical tube portion comprising threeangularly spaced, inwardly projecting hooks 232, shown in FIG. 19, thatcan be pushed over and engage the bulb 256 on the needle shield 250.This ensures that the needle shield is removed with the cap when thedevice is to be used. The cap also comprises three inwardly projectinglugs 234, equally spaced around the circumference on the cap, that areconfigured to engage the lower housing 340. To remove the cap, a usersimply grips and squeezes the cap between two fingers and pulls the capaway from the lower housing. The use of three, equally spaced lugsensures that when the cap is radially squeezed by a user, at least twoof the lugs will move outwardly to disengage from the lower housing,whatever direction the cap is squeezed in. This ensures that the cap canbe easily removed.

FIGS. 28a to 28e are cross-section views of the second embodiment,illustrating the sequence of operation. FIG. 28a shows the deviceimmediately after cap removal, but prior to the pressing of the skinsensor element against an injection site. It can be seen that the needleshield assembly has been removed together with the cap.

FIG. 28b shows the device with the skin sensor 312 element pushed back,compressing the skin sensor spring 314. The bracing arms 318 on the skinsensor element abut the chassis to prevent the skin sensor element frommoving further back. In this position, the latches 322 on the chassisare free to bend out into the windows 315.

FIG. 28c shows the drug container 211 and powerpack housing 264 moved toan insertion position by the expansion of insertion spring 261. In thisposition, the needle 212 is inserted into the injection site. The drivemember 270 is just clear of the locking surface 226 on the outerhousing. This means that legs 274 can be squeezed together to disengagethe lugs 272 from surface 267 on the powerpack housing 264. The drivespring 262 is free to expand. The camming protrusions 269 on thepowerpack housing have deflected the latching elements 324 so that theskin sensor element 312 is free to move forward to a fully extendedposition once it is removed from the injection site.

FIG. 28d shows the drive spring 262 expanded. The sealing foil 216 hasbeen ruptured and the plunger 214 has been moved through the drugcontainer and the drug has been ejected.

FIG. 28e shows the device after it has been removed from the injectionsite, with the skin sensor element in a fully extended position, lockedand covering the needle. The skin sensor element is retained to thechassis and prevented from further forward movement by the engagement ofbracing arms 318 with a portion of the lower housing 340. The lockingarms 316 have flexed to allow the skin sensor element to pass as theskin sensor to the extended position, but surfaces 317 lock the skinsensor element in the extended position, preventing any retraction ofthe skin sensor element.

FIG. 29 is a schematic diagram illustrating the assembly process of anautoinjector in accordance with the second embodiment of the invention.In step 350, the drug container assembly 210, including the needle 212and needle shield 250 is filled with dose of drug and a plunger 214, andthen sealed by a sealing foil 216. This is carried out in a sterileenvironment. Independently, in step 352 the powerpack assembly isassembled to the outer housing. In step 354 the filled drug containerassembly is then fitted to the powerpack assembly. The front end of thedevice, including the chassis, skin sensor element, skin sensor spring,and lower housing is assembled in step 356. The powerpack housingincludes locking arms 266, which are received in openings 224 in theouter housing to retain the insertion spring in a first compressedstate. The locking surface 226 engages the drive member 270 to hold thedrive spring in a compressed state.

In step 358, the front end assembly is coupled to the drug containerassembly and the powerpack assembly and outer housing. The drugcontainer assembly is retained by latching arms on the chassis. Thewindow portions 348 of the lower housing clip into to the windows 222 ofthe outer housing. As the lower housing is moving towards an engagedposition in which the window portions are fully engaged with the windowson the outer housing, the chassis 320 engages the arms 266 on thepowerpack housing to move them out of the openings 224. This mechanismis illustrated in FIG. 30.

The chassis includes cam surfaces 336 at its rear end that engagecorresponding cam surfaces 267 on the locking arms 266. As the chassisand powerpack move toward one other, the cam surfaces 267 on the chassisdeflect locking arms inwardly and out of engagement with the outerhousing 220. At this point, the insertion spring 260 is allowed toexpand a small amount, but it is subsequently held in a secondcompressed state as soon as the lower housing 340 engages the outerhousing. The latches 322 on the chassis engage the drug containerassembly 210, the chassis 320 is fixed to the lower housing and thelower housing is fixed to the outer housing. Accordingly, the insertionspring cannot expand until the latches 322 are released from the drugcontainer. In the second compressed state, the insertion spring stillstores enough energy to insert the needle 12 into an injection site bypushing the drug container to the insertion position when the latches322 are released. The components are configured so that thedisengagement of the locking arms 266 from the outer housing happensonly momentarily before the window portions 348 lock to the window 222.

The cap 30 is typically assembled to the lower housing 340 duringassembly of the front end assembly, but may be added after the powerpackand front assembly are joined or after the outer housing has been fittedto the lower housing. These options are illustrated in FIG. 29 as step357. Also, as an alternative to the process illustrated in FIG. 29, thedrug container assembly could be assembled to the front end assemblybefore being coupled to the powerpack and outer housing. The assemblyprocess is complete at step 360.

What is claimed is:
 1. A drug delivery device comprising: a housing; adrug container within the housing and containing a drug to be dispensed,the drug container having a first end defining a first opening; aplunger, positioned within the drug container, in contact with the drug;a first sealing element providing a first closure seal across the firstopening of the drug container; a pusher initially located on an oppositeside of the first closure seal to the plunger, wherein the pusher isoperable to break the first closure seal and move the plunger within thedrug container to dispense the drug; and an insertion mechanismconfigured to move the drug container through the housing, wherein,prior to use, the pusher and the insertion mechanism are held out ofcontact with the first sealing element.
 2. A drug delivery deviceaccording to claim 1, wherein the drug container comprises a secondopening through which the drug is dispensed and at least one side wallextending between the first opening and the second opening, wherein theinsertion mechanism is engaged to the at least one sidewall.
 3. A drugdelivery device according to claim 1, wherein the plunger is a cup sealtype plunger, configured such that a component of the fluid pressureexerted by the drug on the plunger as the plunger is moved through thedrug container is directed towards a sealing interface between theplunger and an internal surface of the drug container.
 4. A drugdelivery device according to claim 1, wherein a peripheral portion ofthe plunger in contact with a wall of the drug container comprises asubstantially non-elastomeric material.
 5. A drug delivery deviceaccording to claim 1, wherein the first sealing element provides asterile seal.
 6. A drug delivery device according to claim 1, whereinthe pusher comprises one or more piercing elements or serrations on aseal contact surface, configured to pierce the first sealing elementduring operation of the device.
 7. A drug delivery device according toclaim 1, wherein the device is an autoinjector.
 8. A drug deliverydevice comprising: a housing; a drug container within the housing andcontaining a drug to be dispensed, the drug container having a first enddefining a first opening; a plunger, positioned within the drugcontainer, in contact with the drug; a first sealing element providing afirst closure seal across the first opening of the drug container; apusher initially located on an opposite side of the first closure sealto the plunger, wherein the pusher is operable to break the firstclosure seal and move the plunger within the drug container to dispensethe drug; and an insertion mechanism configured to move the drugcontainer through the housing prior to operation of the pusher to breakthe first closure seal, wherein no elements of the insertion mechanismand housing contact the first sealing element as the drug container ismoved through the housing.
 9. A drug delivery device according to claim8, wherein the device is an autoinjector.
 10. A drug delivery device,comprising: a drug container; an internal housing; an insertionmechanism coupled to the drug container and configured to move the drugcontainer through the internal housing in an insertion direction; a skinsensor element, configured to contact an injection site in use; and askin sensor biasing element biasing the skin sensor in the insertiondirection relative to the internal housing; wherein the skin sensorelement is movable relative to the internal housing in a directionopposite to the insertion direction from an initial position to aretracted position to trigger the insertion mechanism; wherein theinternal housing includes a first latching element to restrain the skinsensor element from moving from the initial position in the insertiondirection, wherein the first latching element comprises a latchingsurface to engage the skin sensor element and a first camming surface;and wherein either the drug container or the insertion mechanismincludes a second camming surface, wherein the second camming surface isconfigured to engage the first camming surface to move the firstlatching element as the drug container is moved through the internalhousing, thereby allowing the skin sensor element to move in theinsertion direction past the initial position to an extended position.11. A drug delivery device according to claim 10, wherein the firstlatching element comprises a resilient cantilever arm, wherein thelatching surface and the first camming surface are formed at a free endof the cantilever arm.
 12. A drug delivery device according to claim 11,wherein the resilient cantilever arm is held in tension by the skinsensor element and the skin sensor biasing element when the skin sensorelement is in the initial position.
 13. A drug delivery device accordingto claim 10, wherein the internal housing defines a central bore throughwhich the drug container moves, and wherein the first and second cammingsurfaces are configured to move the latching element in a directionparallel to a perimeter of the bore.
 14. A drug delivery deviceaccording to claim 13, wherein the first camming surface is positionedinwardly of the latching surface.
 15. A drug delivery device accordingto claim 10, wherein the first camming surface extends non-parallel withthe latching surface.
 16. A drug delivery device according to claim 10,wherein the skin sensor element comprises at least a first aperture thataligns with a drug container latch on the internal housing when the skinsensor element is in the retracted position.
 17. A drug delivery deviceaccording to claim 10, wherein the skin sensor is configured so as notto occlude a window in the internal housing for viewing the drugcontainer when in the initial or retracted position.
 18. A drug deliverydevice according to claim 10, further comprising a second latchingelement formed on the internal housing, the second latching elementbeing configured to prevent the skin sensor moving to the retractedposition after it has been released from the first latching element. 19.A drug delivery device according to claim 18, wherein the secondlatching element engages a second aperture or a protrusion on the skinsensor element.
 20. A drug delivery device according to claim 10,wherein in the retracted position the skin sensor element abuts theinternal housing.